This invention relates to a process for bonding together the tubular components of a heat exchanger, the process being particularly well suited for bonding aluminum tubing.
For economic reasons, it has long been desirous in the art to form the tubular components of a fan coil type heat exchanger of aluminum based materials. However, the bonding of aluminum components has heretofore proven to be extremely difficult because of the rapid oxidation that takes place in the joint region during the bonding process. Recently, an ultrasonic dip soldering process was developed which essentially overcomes the oxidation problems. In the dip process, as disclosed by Greever in U.S. Pat. No. 3,760,481, the tubular joints of the heat exchanger are immersed in a molten bath of solder and the bath then treated with ultrasonic energy. The energy is transmitted through the bath into the joint regions to remove rapidly forming oxides created therein. The exchanger is then removed from the bath and the solder cooled in ambient air.
It has been found, however, that the heat exchanger body itself, being specifically designed as a highly efficient heat transfer structure, rapidly pulls heat out of the joint region during the soldering process. This, in turn, causes the solder to be prematurely solidified within the joint region before it can be treated with ultrasonic energy thus negating the advantages associated with the ultrasonic dip process.